(1) Field of the Invention
The present invention relates to the field of water purifiers, and more specifically to improved compound valves for controlling the operation of reverse osmosis water purifying systems.
(2) Prior Art
U.S. Pat. No. 4,176,063 discloses a control valve for a reverse osmosis water purifying system. The valve controls the operation of the system according to the water pressure present in the system's pure water delivery line. The control valve comprises four individual diaphragm valves linked together by hydraulic passages. Two of the valves are in essence double diaphragm valves utilizing diaphragms of substantially different size with a mechanical linkage therebetween so that the desired hydraulic pressure ratios can be achieved.
One of the diaphragm valves is a check valve that maintains pressure in the pure water delivery line between the check valve and the dispensing spigot., The control valve also contains a double diaphragm pilot valve hydraulically linked to the pure water delivery line such that the pilot valve opens when the spigot is opened and the pure water pressure is low. The purifying system typically contains a pure water tank that contains a bladder which pressurizes the pure water therein. The bladder is pressurize by a squeeze water provided by an outlet of the reverse osmosis unit. The control valve has a third squeeze water diaphragm valve which opens in response to the opening of the pilot valve and controls the flow of pressurized waste water from the reverse osmosis unit to the pure water tank. Finally, the control valve contains a fourth diaphragm inlet valve which controls the inflow of water from the main water line to the system. This inlet valve is closed when the pure water tank is completely filled with pure water, to prevent water from flowing through the reverse osmosis unit when the tank no longer requires pure water.
This prior art control valve has subsequently been improved by the addition of two additional valves. The first of these, a duck bill valve, assures that there is always a limited flow of waste water through the reverse osmosis unit to remove salts and other impurities from the unit's filter membrane whenever water is being filtered, a function provided by a separate constriction elsewhere in the system in accordance with the disclosure of the '063 patent. The second additional valve, a diverter valve, allows squeeze water in the pure water tank to flow to a drain to eliminate the back pressure in the pure water during the filtering process.
U.S. Pat. No. 4,885,085 discloses another reverse osmosis water purifier control valve. The purifier valve has a single tap water inlet diaphragm valve that shuts off the inlet tap water when the pure water pressure approaches the tap water line pressure, indicating that the pure water storage tank is full. The '085 control valve also has a direct acting pilot valve that is responsive to the pure water pressure and used to control a squeeze water control valve. Functioning of the valve is very similar to that of the prior art though with a much simplified and more reliable structure.
In all of the foregoing systems, a check valve is required in the line between the pure water outlet of the reverse osmosis unit and the connection to the pure water side of the pure water accumulator tank. For this purpose, a duck bill check valve has been used. These valves are simple in-line valves, but do not have the life and reliability of other parts of the system. A system with a separate check valve is more difficult to service because of uncertainty as to which specific valve may be causing a particular problem. It is therefore more difficult to determine which components should be serviced.
Also in the foregoing systems, the waste water output from the reverse osmosis element is routed directly to the drain line. Therefore the waste water flows during dispensing as well as during purification. This is both wasteful of water and of delivery pressure when dispensing.